1. Field of the Invention
The invention relates to the catalytic polymerization of ethylene, alone, or with other .alpha.-olefin monomers.
2. Description of the Prior Art
U.S. Pat. No. 3,709,853 discloses the use of an inorganic oxide supported bis-cyclopentadienyl chromium [II] compound as a catalyst for the polymerization of ethylene alone, or with other .alpha.-olefins.
U.S. Pat. No. 4,015,059 discloses the use of bis (indenyl)-and bis(fluoroenyl)-chromium [II] compounds deposited on activated inorganic oxide supports to provide catalysts for the polymerization of ethylene in high yields.
Ethylene polymers made with these supported chromium [II] catalysts are susceptible to degradation by thermal and oxidative processes. The severity of this degradation depends upon factors such as, the productivity of the catalyst, the degree of branching of the polymer, the conditions under which the polymer is stored and the conditions under which the polymer is processed.
This degradation can be controlled by the addition of various antioxidants to the polymer during compounding. However, the efficiency of the antioxidant may be diminished because of, for example, poor dispersion of the antioxidant in the polymer and problems of retaining the antioxidant in the polymer after it has been blended into the polymer.